Ophthalmic lenses, in particular contact lenses, are nowadays produced in great volumes in highly automated manufacturing lines. In a packaging station of such manufacturing line the contact lens is placed into a receptacle for the final contact lens packaging. Usually saline is added into the receptacle and a removable cover is placed, for example laminated, on top of the receptacle to provide for a liquid-tight closure of the receptacle containing the contact lens in the saline for the storage and shipment of the package.
In a final detection step it is ascertained that actually one and only one contact lens is present in the receptacle of the contact lens package. One method for detecting whether or not one contact lens and only one contact lens is present within a receptacle is based on fluorescence. In this method, the translucent receptacle is irradiated with ultraviolet radiation stimulating the contact lens material to emit fluorescent light. By detecting the amount of fluorescent light coming from within the receptacle it may be concluded whether or not a contact lens is present within the receptacle. From the amount of detected fluorescent light it may also be concluded if more than one contact lens is contained within the receptacle.
The ultraviolet radiation for the stimulation of fluorescence of the contact lens material has a wavelength smaller than 300 nm. Ultraviolet light sources which emit radiation of wavelengths smaller than 300 nm only have a limited lifetime, which in the case of usually employed UV-LEDs may amount to only some hundred hours. Thus, the ultraviolet light sources must be replaced comparatively frequently, which may interfere with the automated manufacturing process and reduces the efficiency of the manufacturing process. In addition, in order to protect the operating personnel from any irritation caused by the ultraviolet radiation reliable shielding measures must be provided. However, such shielding measures may present a physical obstacle both to the operational procedures and the operating personnel, and leads to an increase of the costs of the manufacturing process. In addition, the method for detection of the contact lens based on fluorescence depends strongly on the material the contact lens is made of. Depending on the lens material, a detection based on fluorescence may not be an option.
It is therefore an object of the invention to provide a method for the detection of an ophthalmic lens, in particular a contact lens within a receptacle which avoids the aforementioned disadvantages and which is technically simple and reliable.